The invention relates to a safety belt arrangement with a belt retractor comprising a force-limiting device that, when triggered in a collision, is associated with a limited release from the blocked retractor.
A generic safety belt arrangement is known from DE 43 31 027 A1. In it, the belt retractor is provided with a force-limiting device that in particular when cooperating with an airbag causes the intentional release of the belt in a controlled manner while simultaneously reducing the force peaks that occur during a collision. If subsequent to such a first collision (primary collision) there is a second collision, e.g. in a multi-vehicle collision, the slack in the belt created by the force-limiting device in the primary collision is disadvantageous because the triggered safety belt no longer holds the occupant wearing the safety belt securely enough.
The object of the invention is therefore to further develop a safety belt arrangement of the type specified in the foregoing so that the person wearing the safety belt is securely restrained even in a second collision subsequent to the primary collision.
This object is achieved, including advantageous embodiments and further developments of the invention, from the contents of the patent claims that follow this specification.
The main idea behind the invention is that associated with the belt retractor is a tautening or tensioning device that is actuated subsequent to the primary collision and that eliminates the slack in the belt that occurs when the force-limiting device is triggered during the primary collision. The invention is associated with the advantage that, despite the slack in the belt necessarily associated with the force-limiting process in a primary collision, the person wearing the belt is securely restrained if there is a second collision because the slack in the belt that is created during the primary collision is immediately eliminated by the additional tensioning apparatus provided in accordance with the invention.
In a first embodiment the invention provides that the tensioning device constitutes an energy accumulator that can be loaded by the rotation of the belt winding shaft in the direction of the belt""s release while the force-limiting device is being triggered, whereby the loadable energy accumulator can especially constitute a tensible spring. Alternative energy accumulators, e.g. in the form of air compression, are also conceivable. This results in the advantage that an additional tensioning apparatus of this type is integrated into the retractor and simultaneously in particular false triggering is not possible because the energy to be stored in the tensioning apparatus is not built up until the force-limiting device is actuated. It can furthermore be provided that the untensed spring is connected to the belt winding shaft and its free spring end can be caused to engage with a stop attached to the housing when the force-limiting device is triggered so that the spring is tensed by the rotation of the belt winding shaft in the direction of the belt""s release, said rotation occurring when a force is limited.
When in accordance with the generic DE 43 31 027 A1 the force-limiting device comprises a torsion bar that is blockably tensed on one side and that at the other end is joined to the winding shaft and the winding shaft is rotatable relative to the tensioning of the torsion bar while the force-limiting device is being triggered, the rotation of the winding shaft is advantageously used for tensing the spring constituting the tensioning device in that a lever arrangement is provided that is arranged between a shaft axis and the free spring end, that in its neutral position holds the spring end free, and that can be moved by the relative movement between the winding shaft and the tensioning of the torsion bar in an extended position that effects engagement of the spring end with the stop attached to the housing.
In a generic belt retractor, in which in the interior of the shaft body of the winding shaft is arranged a shaft casing that is joined on one side to the torsion bar and that can be fixed via the blocking system of the retractor and that encloses the torsion bar, such a lever arrangement can be arranged such that a first lever is borne on the shaft axis and is fixed to the shaft casing via a shearing pin and a second lever guiding the spring end is joined to the first lever and is deflectably arranged via a link guide embodied between the shaft body and the second lever radially outward until it engages the spring end held by the second lever at the stop attached to the housing.
If, in another embodiment of the safety belt arrangement, the force-limiting device comprises a torsion bar joined at its one end to the winding shaft and at its other end connected to a profiled head as carrier of the blocking member and the winding shaft is rotatable relative to the profiled head while the force-limiting device is being triggered, as an alternative to the lever arrangement an apparatus for tensing the spring can be provided that constitutes the tensioning apparatus in which apparatus the spring end is held at a gearwheel movably arranged via a control link at the torsion bar due to the relative movement between the winding shaft and the torsion bar until it engages in a toothed member attached to the housing, whereby the rotation of the winding shaft in the direction of the belt""s release during the force-limiting process tenses the spring via rolling of the gearwheel on the toothed member attached to the housing.
An alternative embodiment of the invention has as its subject a tensioning apparatus arranged outside the retractor, in which tensioning apparatus a drive energy for the secondary tensioning apparatus is to be maintained. In a corresponding exemplary embodiment of the invention it is provided that the retractor is fastened to a movable slide member on a track attached to the vehicle and the tensioning device is embodied as a drive apparatus that acts on the slide member and that eliminates the slack in the belt caused when the slide is displaced with the retractor during a primary collision and that is triggerable subsequent to the primary collision. Depending on the strength of the tensioning apparatus, in addition to eliminating the slack in the belt, the body of an occupant who is, e.g., bent forward can be returned. In accordance with exemplary embodiments of the invention, the drive apparatus can be embodied as pre-tensed compression springs that drive the slide member when triggered or alternatively as a drive apparatus that acts pyrotechnically on the slide member.
Finally, the retractor used in the safety belt arrangement, in addition to being joined to the force-limiting device, can also be joined to a tensioning apparatus for the primary collision, as described in the generic DE 43 31 027, so that two tensioning devices are available in such an embodiment of the invention, and these are one tensioning device for the primary collision and one tensioning device for the secondary collision that is activated by the force-limiting function.